PRPF6 Antibody

What is PRPF6 and what are its primary biological functions?

PRPF6 (pre-mRNA processing factor 6) is a 107 kDa protein with dual cellular roles. Primarily, it functions as a component of the U4/U6-U5 tri-snRNP complex in the spliceosome, where it acts as a bridging factor between U5 and U4/U6 snRNPs during pre-mRNA splicing . Additionally, PRPF6 plays a significant role in transcriptional regulation by enhancing androgen receptor (AR) activity, serving as a coactivator for both full-length AR (AR-FL) and AR variant 7 (AR-V7) . The protein contains an N-terminal domain followed by multiple tetratricopeptide repeat (TPR) motifs that are crucial for its protein-protein interactions . PRPF6 is also known by several other names including ANT-1 (Androgen receptor N-terminal domain-transactivating protein 1), C20orf14, U5-102 kDa protein, and TOM .

What are the validated applications for PRPF6 antibodies?

PRPF6 antibodies have been validated for multiple research applications, with varying specificities and sensitivities depending on the antibody source and clone. The primary validated applications include:

The optimal working concentration varies between antibody sources and should be determined empirically for each experimental system .

How should PRPF6 antibodies be stored and handled for optimal performance?

For maximum stability and antibody performance, PRPF6 antibodies should be stored at -20°C for long-term storage (typically stable for one year after shipment) . For frequent use over short periods (up to one month), storage at 4°C is acceptable to avoid freeze-thaw cycles . Most commercial PRPF6 antibodies are supplied in PBS buffer containing glycerol (typically 50%) and sometimes BSA (0.1-0.5%) with sodium azide (0.02%) as a preservative . If the antibody is provided in lyophilized form, proper reconstitution is critical - typically adding 100 μL of distilled water to achieve a final concentration of 1 mg/mL . Aliquoting is recommended to minimize freeze-thaw cycles for antibodies stored without high glycerol content, as repeated freezing and thawing can significantly reduce antibody activity and specificity .

What positive and negative controls should be used when working with PRPF6 antibodies?

For reliable PRPF6 antibody validation, appropriate controls should include:

Positive Controls:

• HEK-293 cells, HeLa cells, and NIH/3T3 cells have been verified to express detectable levels of endogenous PRPF6 for Western blot applications

• Human testis tissue has been validated for immunohistochemistry applications with PRPF6 antibodies

• CWR22Rv1 and VCaP cells express high levels of PRPF6 compared to LNCaP cells in prostate cancer models

Negative Controls:

• PRPF6 knockdown samples using validated siRNAs or shRNAs provide excellent negative controls for antibody specificity testing

• Secondary antibody-only controls are essential to rule out non-specific binding

• Peptide competition assays using the immunizing peptide can verify antibody specificity

Pre-immune serum controls from the same host species are also valuable for polyclonal antibodies to distinguish specific from non-specific signals .

How can researchers effectively detect PRPF6 interaction with androgen receptor (AR) in experimental systems?

To investigate PRPF6-AR interactions, researchers should employ multiple complementary approaches:

Co-immunoprecipitation (Co-IP):

• Use anti-PRPF6 antibodies (0.5-4.0 μg for 1-3 mg of total protein lysate) to precipitate protein complexes from nuclear extracts of cells expressing AR

• Perform reciprocal Co-IPs using anti-AR antibodies to confirm interactions

• Include both DHT-treated and untreated conditions, as the interaction occurs in both states but is enhanced with DHT treatment

Domain Mapping:
Research has shown that the interaction between PRPF6 and AR requires the first 5 TPR motifs (309-463 aa fragment) in PRPF6 . Truncation mutants can be used to confirm interaction domains:

• PRPF6-FL (full length)

• PRPF6-N (1-308 aa)

• PRPF6-C (309-941 aa)

• PRPF6-5TPR (1-482 aa)

• PRPF6-10TPR (1-640 aa)

• PRPF6-15TPR (1-809 aa)

Immunofluorescence Co-localization:
Nuclear co-localization should be visualized by immunofluorescence, as endogenous PRPF6 localizes to the nucleus in prostate cancer cells including LNCaP, CWR22Rv1, and DU145 . In LNCaP cells, PRPF6 is compartmentalized in the nucleus with AR under DHT treatment .

Functional Validation:
Luciferase reporter assays using ARE-luc, MMTV-tk-luc, or PSA-tk-luc reporters can confirm the functional relevance of the interaction by demonstrating that PRPF6 enhances AR-mediated transcription .

What are the best approaches for analyzing PRPF6 expression in tumor samples and what patterns should researchers expect?

For comprehensive analysis of PRPF6 expression in tumor samples, researchers should combine multiple approaches:

Immunohistochemistry Protocol:

• Use formalin-fixed paraffin-embedded tissue sections with appropriate antigen retrieval (TE buffer pH 9.0 or citrate buffer pH 6.0)

• Apply PRPF6 antibody at 1:20-1:200 dilution depending on the specific antibody

• Score using the Hscore method: intensity scored as 0 (negative), 1 (weak), 2 (moderate), or 3 (strong), then multiplied by the proportion of positive cells to generate a final score ranging from 0-3

Expression Patterns in Cancer:

• In prostate cancer: PRPF6 is highly expressed in human prostate cancer samples compared to adjacent normal tissues

• In hepatocellular carcinoma (HCC): PRPF6 expression is positively correlated with pathological grade, with expression intensity gradually increasing with higher grades

• In HCC, PRPF6 expression in male samples is comparable to female samples, suggesting sex-independent regulation

Prognostic Value:
Higher PRPF6 expression has been correlated with poor prognosis in HCC, suggesting its potential as a prognostic biomarker . Statistical analysis using Student's t-test can determine significant differences between immunohistochemical expression of PRPF6 in cancer versus normal tissues .

What troubleshooting strategies should be employed when PRPF6 antibodies show nonspecific binding or weak signals?

When facing technical challenges with PRPF6 antibodies, researchers should implement these systematic troubleshooting strategies:

For Nonspecific Binding:

• Increase blocking stringency using 5% BSA or 5% milk in TBS-T for Western blots

• Optimize primary antibody dilution by testing a wider range (e.g., 1:250-1:4000 for WB)

• Reduce incubation time or temperature for primary antibody

• Increase washing steps (5-6 washes of 5-10 minutes each)

• Include a validated peptide competition control using the immunizing peptide to confirm specificity

For Weak Signals:

• Test different antigen retrieval methods for IHC (TE buffer pH 9.0 is recommended but citrate buffer pH 6.0 may be an alternative)

• Increase antibody concentration or incubation time

• Use a more sensitive detection system (e.g., polymer-based detection versus ABC method for IHC)

• For WB, load more protein (50-100 μg) and consider using enhanced chemiluminescence (ECL) substrates with higher sensitivity

• Ensure protein transfer efficiency with a reversible stain before blocking

Additional Considerations:

• Verify the expected molecular weight (approximately 100-107 kDa)

• Test multiple PRPF6 antibodies targeting different epitopes, as epitope accessibility may vary between applications and sample preparation methods

• For recalcitrant tissues, consider specialized fixatives or alternative sample preparation methods

How can researchers effectively study PRPF6's dual roles in splicing and transcriptional regulation?

To dissect PRPF6's functions in both splicing and transcriptional regulation, researchers should employ targeted approaches:

For Splicing Function:

• RNA-seq analysis following PRPF6 knockdown to identify global alternative splicing events

• RT-PCR validation of specific splice variants of interest, especially those relevant to cancer (e.g., AR-V7)

• Co-IP with splicing components to confirm PRPF6's interaction with U4/U6-U5 tri-snRNP complex components

• Minigene splicing assays to test direct effects on specific splicing events

For Transcriptional Regulation:

• Chromatin immunoprecipitation (ChIP) to detect PRPF6 recruitment to AR target genes:

  • Use anti-PRPF6 antibodies to immunoprecipitate chromatin

  • Examine enrichment at androgen responsive elements (AREs) in genes like PSA, KLK2, FASN, TMPRSS2, UBE2C

  • Include appropriate controls (IgG, input)

• Sequential ChIP (Re-ChIP) to demonstrate co-occupancy of PRPF6 and AR on target gene promoters

• Evaluate histone modifications: PRPF6 depletion abrogates H3K36me3 modification at the ARE region of the AR gene

Functional Separation Approaches:

• Generate domain-specific mutants that selectively disrupt one function while preserving the other

• For example, PRPF6-5TPR and PRPF6-10TPR enhance AR-FL-mediated transactivation similar to full-length PRPF6, while neither PRPF6-N nor PRPF6-C have significant effects

• Use selective inhibitors of splicing versus transcription to determine which function is more critical for observed phenotypes

What criteria should guide selection of the appropriate PRPF6 antibody for specific research applications?

When selecting a PRPF6 antibody for specific applications, researchers should consider these critical parameters:

Epitope Location:
Different antibodies target distinct regions of PRPF6, which affects their utility in specific applications:

• Antibodies targeting the N-terminal domain (aa 1-50): Useful for detecting full-length protein but may miss truncated forms

• Antibodies targeting the C-terminal region (aa 747-796): Better for detecting potential splice variants

• Antibodies against the TPR motifs: Critical for studying protein-protein interactions, especially with AR

Validation Status:
Select antibodies with comprehensive validation data relevant to your experimental system:

• Check if the antibody has been validated in knockout/knockdown systems

• Review published literature citing the specific antibody catalog number

• Prioritize antibodies with orthogonal validation methods (e.g., RNAseq correlation)

Species Reactivity:
While most PRPF6 antibodies react with human, mouse, and rat samples, sequence conservation varies across different regions of the protein . For cross-species studies, select antibodies targeting highly conserved epitopes and validate reactivity in each species of interest.

Application-Specific Considerations:

• For ChIP experiments: Select antibodies validated for immunoprecipitation and targeting epitopes not involved in DNA binding

• For studying protein interactions: Avoid antibodies whose epitopes might interfere with interaction domains (first 5 TPR motifs, 309-463 aa)

• For detecting post-translational modifications: Ensure the antibody specificity is not affected by nearby modifications

Clonality Considerations:
While most available PRPF6 antibodies are polyclonal, each has different specificity profiles. Testing multiple antibodies from different vendors can help confirm findings and rule out antibody-specific artifacts .

What are the optimal protocols for using PRPF6 antibodies in chromatin immunoprecipitation (ChIP) studies?

For successful PRPF6 ChIP experiments, researchers should follow this optimized protocol:

Sample Preparation:

• Crosslink cells with 1% formaldehyde for 10 minutes at room temperature

• Quench with 0.125 M glycine for 5 minutes

• Wash cells with cold PBS twice

• Collect 5-10 million cells per ChIP reaction

• Lyse cells and isolate nuclei using appropriate buffers

Chromatin Preparation:

• Sonicate chromatin to generate fragments of 200-500 bp

• Verify fragment size by agarose gel electrophoresis

• Pre-clear chromatin with protein A/G beads and non-specific IgG

Immunoprecipitation:

• Use 2-5 μg of validated PRPF6 antibody per ChIP reaction

• Include appropriate controls:

  • IgG from same species as negative control

  • Antibody against known AR-associated proteins (e.g., JMJD1A) as positive control

• Incubate overnight at 4°C with rotation

• Add protein A/G beads and incubate 2-4 hours

• Perform stringent washing steps (low salt, high salt, LiCl, and TE buffers)

DNA Recovery and Analysis:

• Elute protein-DNA complexes and reverse crosslinks (65°C overnight)

• Treat with RNase A and proteinase K

• Purify DNA using column-based methods

• Analyze by qPCR targeting specific genomic regions:

  • ARE regions of AR target genes (PSA, KLK2, FASN, UBE2C)

  • ARE region of the AR gene itself to study self-transcription

  • Negative control regions (gene deserts)

Data Analysis:
Calculate enrichment as percentage of input or fold enrichment over IgG control. PRPF6 has been shown to be recruited to cis-regulatory elements in AR target genes, and it associates with JMJD1A to enhance AR-induced transactivation .

How can researchers effectively design PRPF6 knockdown experiments to study its function in cancer models?

To design robust PRPF6 knockdown experiments in cancer models, researchers should implement these methodological approaches:

siRNA/shRNA Design:

• Design multiple siRNAs targeting different regions of PRPF6 mRNA to minimize off-target effects

• Previously validated siRNA sequences include:

  • siPRPF6#1, #2, and #3 have been tested in HCC cells

  • Lentivirus-mediated knockdown has been successful in prostate cancer cell lines

• Include appropriate controls:

  • Non-targeting siRNA with similar GC content

  • GAPDH or other housekeeping gene siRNA as positive control

Validation of Knockdown Efficiency:

• Verify knockdown at mRNA level using qRT-PCR (>70% reduction is desirable)

• Confirm protein reduction by Western blot using validated PRPF6 antibodies

• Assess both short-term (48-72h) and long-term (stable shRNA) knockdown effects

Phenotypic Assays:
Based on published data, these assays are most relevant for PRPF6 function in cancer:

• Cell Proliferation/Growth:

  • Colony formation assays have shown PRPF6 knockdown impairs colony formation in CWR22Rv1 and LNCaP cells

  • Cell growth curves show slower growth in PRPF6 knockdown cells

• Gene Expression Analysis:

  • qRT-PCR for AR target genes: PSA, KLK2, FASN, TMPRSS2, UBE2C, BMPRIB, HPGD, SLC45A3, ACPP

  • For HCC models: CCRK, PRC1, VEGFA, and FKBP5

• In vivo Xenograft Models:

  • CWR22Rv1 cells with PRPF6 knockdown showed reduced tumor burden, smaller volumes, and slower growth rates in mouse xenograft models

  • Include castration conditions to test AR-dependent effects

Rescue Experiments:
To confirm specificity, perform rescue experiments with:

• Expression of siRNA-resistant PRPF6 cDNA (with silent mutations in the siRNA target site)

• Domain-specific constructs to identify which PRPF6 domains are necessary for specific functions

• AR overexpression, which has been shown to rescue growth inhibition caused by PRPF6 knockdown in CWR22Rv1 cells

What experimental approaches can distinguish between PRPF6's effects on AR-full length versus AR splice variants in cancer models?

To differentiate PRPF6's effects on AR-full length (AR-FL) versus AR variants (particularly AR-V7), researchers should implement these specialized approaches:

Cell Model Selection:

• Use multiple cell models with different AR expression profiles:

  • LNCaP: Expresses AR-FL but not AR-Vs

  • CWR22Rv1 and VCaP: Express both AR-FL and AR-Vs

  • Engineered cell lines with specific AR variant expression

Hormone Manipulation:

• Compare conditions with and without dihydrotestosterone (DHT):

  • AR-FL is DHT-dependent

  • AR-V7 is constitutively active without DHT

  • PRPF6 enhances AR-FL-mediated transactivation in the presence of DHT and AR-V7-mediated activity in the absence of DHT

Target Gene Analysis:
Analyze different classes of AR target genes:

• AR-FL-specific targets: Genes predominantly activated by ligand-bound AR-FL

• AR-V7-specific targets: Genes uniquely regulated by AR-V7 (e.g., UBE2C)

• Shared targets: Genes regulated by both AR-FL and AR-V7

Reporter Assays:
Employ luciferase reporter systems with different promoters:

• ARE-luc, MMTV-tk-luc, and PSA-tk-luc reporters show that PRPF6 enhances:

  • AR-FL-mediated transactivation in the presence of DHT

  • AR-V7-mediated transcriptional activity in the absence of DHT

Domain-Specific Effects:
Test which PRPF6 domains are required for effects on different AR forms:

• PRPF6-5TPR and PRPF6-10TPR enhance AR-FL-mediated transactivation similar to full-length PRPF6

• PRPF6-15TPR shows significant enhancement of AR-FL-mediated transactivation

• Neither PRPF6-N nor PRPF6-C have obvious effects

Castration-Resistant Models:
In castration-resistant models (in vitro or in vivo), assess whether PRPF6 depletion affects tumor growth by targeting AR-V7:

• PRPF6 depletion reduces tumor growth in prostate cancer cell lines and suppresses xenograft tumors even under castration conditions

How should researchers interpret discrepancies in PRPF6 antibody results between different applications or cancer models?

When encountering discrepancies in PRPF6 antibody results across different experimental systems, researchers should systematically evaluate several possible explanations:

Technical Factors:

• Epitope accessibility: Different sample preparation methods may affect epitope exposure. For example, formalin fixation may mask epitopes that are accessible in fresh-frozen samples .

• Antibody specificity: Different antibodies target distinct PRPF6 epitopes. Verify antibody epitope locations and compare results with multiple antibodies targeting different regions .

• Application-specific optimizations: Conditions optimal for WB may differ from those for IHC or IP. For instance, antigen retrieval with TE buffer pH 9.0 is recommended for IHC, but alternative methods might be needed for specific tissues .

Biological Variations:

• Splice variants: PRPF6 may have tissue-specific splice variants that affect antibody recognition. RNA-seq data can help identify potential variant expression .

• Post-translational modifications: PTMs may mask epitopes in a cell type-specific manner. For example, phosphorylation states might differ between cancer types .

• Protein-protein interactions: PRPF6 interactions (e.g., with AR) might shield certain epitopes in specific cellular contexts .

Cancer Model Differences:

• Baseline expression levels: PRPF6 is expressed at different levels across cell types. CWR22Rv1 and VCaP cells show higher PRPF6 expression than LNCaP cells in prostate cancer models .

• Hormone dependency: PRPF6 function differs in hormone-dependent versus hormone-independent contexts, affecting its expression and localization patterns .

• Mutation status: Mutations like p.Arg729Trp can affect PRPF6 function and potentially antibody recognition .

Validation Approaches:
To resolve discrepancies, implement multiple validation strategies:

• Use orthogonal detection methods (e.g., mass spectrometry)

• Employ genetic approaches (siRNA/shRNA) to confirm signal specificity

• Test correlation between protein and mRNA levels

• Compare results across multiple antibody sources and clones

What evidence links PRPF6 expression patterns to clinical outcomes in cancer patients, and how should this data be analyzed?

The relationship between PRPF6 expression and clinical outcomes represents an important translational aspect of PRPF6 research:

Current Clinical Evidence:

• Prostate Cancer:

  • PRPF6 is highly expressed in human prostate cancer samples compared to adjacent non-cancerous tissues

  • Implicated in castration-resistant prostate cancer progression through enhancement of AR and AR-V7 activity

  • PRPF6 depletion significantly suppresses xenograft tumors even under castration conditions in mouse models

• Hepatocellular Carcinoma (HCC):

  • PRPF6 expression positively correlates with pathological grade in HCC

  • Higher PRPF6 expression correlates with poor prognosis in HCC patients

  • No significant association was found with other clinical features beyond pathological grade

• Ovarian Cancer:

  • PRPF6 has been implicated in promoting metastasis and paclitaxel resistance through the SNHG16/CEBPB/GATA3 axis

Analytical Approaches:
For robust clinical correlation analysis, researchers should:

How can researchers design experiments to investigate the potential of PRPF6 as a therapeutic target in cancer?

To evaluate PRPF6's potential as a therapeutic target, researchers should implement a comprehensive experimental strategy:

Target Validation Studies:

• Genetic Approaches:

  • Compare effects of PRPF6 knockdown in cancer cells versus normal cells to assess therapeutic window

  • Use inducible shRNA systems to model temporal aspects of therapeutic inhibition

  • Apply CRISPR/Cas9 to generate partial loss-of-function mutants that mimic drug effects

• Domain-Specific Inhibition:

  • Target specific domains of PRPF6 that mediate cancer-relevant functions:

    • First 5 TPR motifs (309-463 aa) required for AR interaction

    • PRPF6-15TPR shows significant enhancement of AR-FL-mediated transactivation

  • Evaluate differential effects of targeting splicing function versus transcriptional coactivator function

Preclinical Models:

• In Vitro Models:

  • Cell line panels representing diverse cancer types and molecular subtypes

  • Patient-derived organoids to capture tumor heterogeneity

  • 3D culture systems to better recapitulate tumor microenvironment

• In Vivo Models:

  • Xenograft models showed PRPF6 depletion reduces tumor burden, with smaller volumes and slower growth rates

  • Include castration conditions to test efficacy in hormone-independent settings

  • Patient-derived xenograft (PDX) models for higher clinical relevance

  • Genetically engineered mouse models (GEMMs) that recapitulate disease progression

Combination Strategies:

• With AR-Targeting Therapies:

  • Since PRPF6 enhances AR signaling, test combinations with:

    • Androgen synthesis inhibitors (e.g., abiraterone)

    • AR antagonists (e.g., enzalutamide)

    • Agents targeting AR degradation

• With Splicing Modulators:

  • Evaluate synergy with splicing inhibitors, particularly those affecting AR-V7 production

  • Test combinations targeting other components of the spliceosome

Biomarker Development:

• Develop predictive biomarkers for PRPF6-targeting therapies:

  • AR/AR-V7 expression levels

  • PRPF6 expression thresholds

  • Dependency on specific PRPF6-regulated splicing events

• Monitor treatment effects through:

  • Changes in AR target gene expression (PSA, KLK2, FASN, etc.)

  • Alterations in specific splice variants

  • Modified histone marks at AR target genes (H3K36me3)

What are the best experimental designs to study PRPF6's role in treatment resistance mechanisms, particularly in castration-resistant prostate cancer?

To investigate PRPF6's contribution to treatment resistance, particularly in castration-resistant prostate cancer (CRPC), researchers should implement these specialized experimental designs:

Model Systems for Resistance Studies:

• Paired Sensitive/Resistant Cell Lines:

  • Compare PRPF6 expression and function in:

    • Parental LNCaP versus enzalutamide-resistant derivatives

    • Hormone-sensitive versus castration-resistant xenografts

  • Develop new resistant models through long-term culture in the presence of AR-targeting therapies

• Clinical Samples:

  • Analyze matched pre-treatment and post-progression tumor samples

  • Compare PRPF6 expression/function in primary versus metastatic CRPC

  • Use tissue microarrays with annotated treatment histories

Mechanistic Investigations:

• AR Splice Variant Regulation:

  • Determine if PRPF6 directly influences AR-V7 splicing in addition to its coactivator function

  • Quantify AR-FL versus AR-V7 ratios following PRPF6 manipulation

  • Perform RNA-seq to identify global splicing alterations in resistant models

• AR-Independent Mechanisms:

  • Investigate PRPF6's effects on cell survival pathways beyond AR signaling

  • Determine if PRPF6 influences alternative resistance mechanisms like glucocorticoid receptor upregulation

  • Assess impact on DNA damage response and repair pathways

Functional Assays:

• Drug Response Profiling:

  • Measure changes in IC50 values for AR-targeting therapies after PRPF6 modulation

  • Use colony formation assays with chronic drug exposure

  • Implement 3D spheroid models that better reflect in vivo drug response

• Pathway Analysis:

  • ChIP-seq to identify PRPF6-regulated enhancers/promoters in resistant cells

  • Phosphoproteomics to uncover PRPF6-dependent signaling changes

  • Metabolomic analysis to identify altered metabolic dependencies

Therapeutic Implications:

• Timing of Intervention:

  • Test PRPF6 inhibition as a strategy to prevent versus reverse resistance

  • Evaluate intermittent versus continuous targeting strategies

  • Study sequential versus concurrent combination approaches

• Predictive Biomarkers:

  • Develop PRPF6 expression/activity signatures that predict treatment response

  • Identify threshold levels of PRPF6 required for resistance mechanisms

  • Test circulating biomarkers that reflect PRPF6-dependent resistance

The existing evidence shows that PRPF6 depletion reduces tumor growth in prostate cancer-derived cell lines and significantly suppresses xenograft tumors even under castration conditions in mouse models . This suggests PRPF6 inhibition might be particularly valuable in CRPC contexts where AR-V7 drives treatment resistance.